Solidus: Rails 6.1 compatibility

[elia]

The latest rails-master introduced some changes that broke the CI for any PR. Solidus should be upgraded in order to take those changes into account. ~Additionally rails@master can be allowed to fail without blocking merges.~ _It's already the case, although the red mark can't be removed._

In this context we should prep for the upcoming release of Rails 6.1.

Solidus Version:
master

To Reproduce

Just look at any recent CI run, the typical error looks like this:

ArgumentError:
  wrong number of arguments (given 3, expected 2)
./lib/spree/testing_support/factories/variant_factory.rb:25:in `block (4 levels) in <top (required)>'
./lib/spree/testing_support/factories/stock_package_factory.rb:25:in `block (5 levels) in <top (required)>'
./lib/spree/testing_support/factories/stock_package_factory.rb:19:in `block (3 levels) in <top (required)>'
./spec/models/spree/calculator/shipping/flat_rate_spec.rb:14:in `block (2 levels) in <module:Shipping>'

https://app.circleci.com/pipelines/github/solidusio/solidus/1517/workflows/7e34a2fa-bf02-46bc-953c-b9f8d9eedcd7/jobs/20534

(the affected factory may vary, and the issue may well may be in factory_girl, but that needs to be verified)

[aldesantis]

@kennyadsl I think you had investigated this issue in the past, right?

[kennyadsl]

Not yet: in the past, we had different errors, mainly related to our dependencies that are still not ready for rails master. This looks new to me.

[filippoliverani]

I think all the current errors are related to Ransack, their latest version and their main are not compatibile with Rails main/6.1RC1 yet.

• We opened an issue for NoMethodError: undefined method 'construct_tables!' but we haven't received any response

• The ArgumentError: wrong number of arguments (given 3, expected 2) error is still related to Ransack Polyamorous joins not being compatible with Rails 6.1

[filippoliverani]

We have a problem with CanCanCan too: undefined method 'resolve_column_aliases' for`, but it has already been addressed here

[filippoliverani]

Ransack main branch is now compatible with Rails 6.1.0.RC1 ❤️